In this study, we propose a revised structural model for highly ordered synthetic Ge-akagané
ite, a stable analogue of tunnel-type Fe-oxyhydroxide, based on the Rietveld refinement of synchrotron X-ray diffraction data and density functional theory with dispersion correction (DFT-D) calculations. In the proposed crystal structure of Ge-akagané
ite, Ge is found not only in the tunnel sites as GeO(OH)3&minus
tetrahedra, but also 4/5 of total Ge atoms are in the octahedral sites substituting 1/10 of Fe. In addition, the tunnel structures are stabilized by the presence of hydrogen bonds between the framework OH and Cl&minus
species, forming a twisted cube structure and the GeO(OH)3&minus
tetrahedra corner oxygen, forming a conjugation bond. The chemical formula of the synthetic Ge-akagané
ite was determined to be (Fe7.2Ge0.8)O8.8(OH)7.2Cl0.8(Ge(OH)4)0.2.